The paper presents the most important data on temperature and other microclimate conditions (solar radiation and light regime) in the 127 year old even-aged pure sessile oak forest in the National Park ?Fruska Gora? in Serbia. Data collection was conducted in July 2008, using an automatic weather station ?WS-GP1? and a luxmeter with a selenium photocell. The study stands are located on the east and west facing sides of a ridge at an altitude of 475m. The slope inclination is 27? and 32?. The canopy is sparse to complete (0.6 to 0.7). The paper presents comparative research results for the eastern and western aspect, which are further compared with the data from the reference weather station ?Rimski Sancevi?. The intensity and trend of microclimate changes depend on the type of forest, its structure, geographical location, canopy closure and other features. Microclimate research results indicate that during the research period the maximum air temperature of the eastern aspect was 24.8?C, which was 3.6?C below the maximum measured at the reference station. The maximum air temperature of the western aspect amounted to 31.0?C, which was 2.8?C below the value measured in the open. The maximum total solar radiation of the eastern aspect was 769W/m2 (at 11.08), and 634W/m2 (at 15.31) of the western. The research determined that the east-facing stand had the light intensity of 6,766.3Lx/m2, while the light transmission coefficient amounted to 14.8%; the west-facing stand had the light intensity of 9213.8Lx/m2 and the light transmission coefficient of 19.3%.